Steven Wolff

Studies on the photochemical reactions of .alpha.,.beta.-acetylenic ketones with tetramethylethylene

Photolyse de melanges de pentyne-3one-2 et de tetramethylethylene dans C 6 H 6 conduisant aux cis- et trans-ethylidene-4 methylene-5 tetramethyl-2,2,3,3 tetrahydrofuranne se transposant en vinyldihydrofuranne et en oxetanne. Mecanisme: mise en jeu de carbenes

3(2H)-Furanones from mercuric acetate oxidation of allenic ketones. A synthesis of bullatenone

Abstract Treatment of allenic ketones 1 ˜ with mercuric acetate yields 3(2 H )-furanones 2 ˜ (90+%). The oxidation of 1 ˜ c ˜ constitutes a new synthesis of bullatenone ( 2 ˜ c ˜ ) .

Synthesis of [4.4.5.5]fenestrane

Abstract Intramolecular photochemical [2 + 2] cyclization of 3b gives 4b regio- and stereospecifically, along with fragmentation product 12b. The Cl atom of 4b was removed by ketalization, Li-NH3 reduction, and reoxidation with RuO4 to furnish 17b. The derived diazoketone 17d on treatment with rhodium(II) acetate underwent cyclization to the [4.4.5.5] fenestrane keto ketal 15. Subsequent reductions gave monoketone 23 and ultimately the parent hydrocarbon 6.

Wavelength Dependency in the Photochemistry of 5-methyl-1,5-hexadien-3-one

Abstract α-Cleavage is the dominant process in 1 ˜ at λ∼313 nm, but 1,5 and 1,6 closure dominate at λ>340 nm. Unlike various more complex carbonyl-substituted hexadienes 3 ˜ − ˜ 5 ˜ , reactions of 1 ˜ can be neither quenched nor triplet-sensitized, thus appearing to emanate from S1 and/or T2.

Light-induced reactions of 1,1,1-trifluoro-3-decyn-2-one with olefins

Abstract Irradiation ( λ = 300 nm) of 1,1,1-trifluoro-3-decyn-2-one in the presence of olefins affords RH-reduction products (tertiary alcohols) in addition to [2+2] -(oxetans) and [3+2] -(dihydrofurans) cycloadducts.

Intramolecular photocyclization of 1-(trimethylsilyl)-1,5-hexadien-3-ones

Abstract An influence upon the regiochemistry of cyclization due to a 1-trimethylsilyl substituent is indicated upon comparison of the photochemistry of 4a,b and their carbon analogs 5a,b.

Photochemistry of 7-syn-isobutylnorborn-2-en-2-yl methyl ketone. Intramolecular hydrogen abstraction in an α,β-unsaturated ketone with geometrically equivalent α- and β-carbon atoms

Preparation and photolysis of 7-syn-isobutylnorborn-2-en-2-yl methyl ketone (7) and its deuteriated isomer (8) are described. Irradiation of (7) in its n,π* band (λ > 3 400 A) leads to two volatile isomers (11)(55%) and (13)(10%), whilst (8) gives (11d) and (13d). The same products were obtained on irradiation of (7) and (8) in the π,π* band (λ > 2 500 A), along with two additional ketones, the photoreduction product (16) and the dienone (25). These results indicate that isomerization of (7) occurs through hydrogen abstraction by the β-carbon atom of the enone system, but not the α-carbon atom. Thus minimization of stereochemical and geometric differences between α and β carbons relative to the abstractable hydrogen does not suffice to elicit abstraction at both centres. The structure of the brexane photoproduct (13) was secured through independent synthesis from olefinic ester (38a). Synthesis of (7), (8), and (13) made use of the novel reaction of a norbornene with trichloroacetyl isocyanate to form an unsaturated nitrile [as (31)→(34) and (38)→(39)].

The photochemistry of two rigid β,γ-cyclopropyl ketones, exo- and endo-tricyclo[3,2,1,02,4]octan-6-one

Photochemical rearrangement of ketones (3) and (9) to bicyclo-octenones (5) and (11), respectively, can be explained by α-cleavage to (12) and (13), followed by stereoelectronically controlled opening to (14) and (15), and then collapse to products.

Synthesis of methyl 1-methyltetracyclo[4.3.1.03,10.08,10]decane-7-carboxylate, a derivative of[4.4.4.5]fenestrane

Photolysis of dienone (7)furnishes(9a), which by way of the diazoketone (12)is cyclized to the difunctionalized [4.4.5.5]fenestrane (13); conversion into(17) and subsequent Wolff rearrangement gives (18a)and(18b); the latter, major isomer is the first [4.4.4.5]fenestrane to be characterized.

Synthesis of Bicyclo[2.2.1]heptan-2-ones by thermal cyclization of 3-allylcyclopentanones

Cyclopentenon (I) liefert mit Allylgrignardverbindung ein Addukt (II), das nach Allylumlagerung und Oxidation das 3-Allyl-2-cyclopentenon (III) gibt.